Autonomous mobile work system comprising a variable reflectivity base station

ABSTRACT

The disclosed technology relates to a method and system for localizing and confining an autonomous mobile work system or systems for performing work in a user defined space is disclosed. The system can include two or more variable reflective base stations at first and second locations that can modify their optical or electromagnetic reflectivity based upon either an external command via wired or wireless communications interface, or automatically on a regular or asynchronous time schedule under programmed or user settable control. The system also can include one or more autonomous mobile work systems capable of sensing the state of the variable reflectance base stations via sensors such as electromagnetic or optical sensors capable of measuring distance to the reflective base stations.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the priority filing benefit of International PCTApplication PCT/US2014/030863 filed Mar. 17, 2014, and published underPCT 21(2) in the English language and U.S. Provisional PatentApplication Ser. No. 61/801,724 filed Mar. 15, 2013. Each of the abovelisted applications is incorporated herein by reference.

FIELD OF THE INVENTION

The disclosed technology relates generally to localization and controlof an autonomous mobile work system, and, more particularly, to a lowcost localization method and system for controlling position of anautonomous mobile work system relative to reflective base stations.

BACKGROUND OF THE INVENTION

In the past, many methods and systems for the localization of anautonomous mobile work system have been proposed and implemented. Theseinclude systems relying upon technologies such as dead reckoning,odometers, inertial navigation systems, satellite based positioningsystems, active beacons, RFID, magnetic compasses and variousterrestrial radio location systems. However, these systems have provenover time to be too unreliable, expensive or complex for use in consumerproducts.

BRIEF SUMMARY OF THE INVENTION

Aspects of the disclosed technology relate to a system and method forlocalizing and confining an autonomous mobile work device or devices toa user-defined space. The system includes at least one autonomous mobilework device that is configured to interact with one or more variablereflective base stations. Through interaction with the variablereflective base stations, the disclosed system provides a cost-effectiveway to localize an autonomous mobile work device by determining distanceto external variable reflectors.

One aspect of the disclosed technology relates to an autonomous mobilework system for performing work in a designated area, the systemcomprising: at least one variable reflectivity base station, the basestation being configured to change its optical and/or electromagneticreflectivity in response to an external command and/or according to apredetermined time schedule; and a mobile work device including at leastone sensor configured to locate the at least one variable reflectivitybase station, wherein the mobile work device is configured to determinea distance between the mobile work device and the at least one variablereflectivity base station.

According to one feature, the mobile work device includes a variablereflectivity indicator, the mobile work device being configured tochange its optical and/or electromagnetic reflectivity.

According to one feature, the at least one base station includes asensor configured to detect the variable reflectivity indicator of themobile work device.

According to one feature, the mobile work device includes a wirelesscommunication interface, and wherein the mobile work device isconfigured to transmit a command to the at least one variablereflectivity base station to change its optical and/or electromagneticreflectivity.

According to one feature, the at least one variable reflectivity basestation includes a wireless communication interface, and wherein the atleast one variable reflectivity base station is configured to receivewireless signals from the mobile work device.

Another aspect of the disclosed technology relates to a mobile workdevice configured to perform work within a predetermined area, themobile work device comprising: at least one sensor configured to locatea variable reflectivity base station located in proximity to thepredetermined area, wherein the mobile work device is configured todetermine a distance between the mobile work device and the at least onevariable reflectivity base station.

According to one feature, the mobile work device includes a variablereflectivity indicator, the mobile work device being configured tochange its optical and/or electromagnetic reflectivity.

According to one feature, the mobile work device includes a wirelesscommunication interface, and wherein the mobile work device isconfigured to transmit a command to the at least one variablereflectivity base station to change its optical and/or electromagneticreflectivity.

Another aspect of the disclosed technology relates to a base stationconfigured to communication with a mobile work device within apredetermined work area, the base station comprising: a variablereflectivity base indicator, the base station being configured to changeits optical and/or electromagnetic reflectivity in response to anexternal command and/or according to a predetermined time schedule.

According to one feature, the base station includes a sensor configuredto detect a variable reflectivity indicator associate with the mobilework device.

According to one feature, the base station includes a wirelesscommunication interface, and wherein the at least one variablereflectivity base station is configured to receive wireless signals fromthe mobile work device.

Another aspect of the disclosed technology relates to an autonomousmobile work system for performing work in a user selected area, thesystem comprising: a mobile work device including a sensor configured tolocate a variable reflectivity base station and measure the distance tosaid base station; and at least one variable reflectivity base station.

According to one feature, the system includes at least one charging basestation.

According to one feature, the system includes a plurality of basestations, wherein at least one of the plurality of base stations is acharging base station.

Another aspect of the disclose technology relates to a unified workapparatus comprising: an autonomous mobile work device comprised of asensor configured to locate a variable reflectivity base station andmeasure the distance to said base station; and at least one variablereflectivity base station.

According to one feature, the apparatus includes at least one chargingbase station.

Another aspect of the disclosed technology relates to a method ofdetermining the location of an autonomous mobile work device, the methodcomprising: providing a first and second variable reflectivity basestation and an autonomous mobile work device, wherein said autonomousmobile work device is configured to determine a distance between saidbase station and said autonomous mobile work system; providing thelocation and orientation of a first variable reflective base station tosaid autonomous mobile work device; providing the location andorientation of a second variable reflective base station to saidautonomous mobile work device; changing the reflectivity state of saidfirst base station; calculating the distance between said first basestation and said autonomous mobile work system; changing thereflectivity state of said second base station; calculating the distancebetween said second base station and said autonomous mobile work system;and calculating the location of said autonomous mobile work system usingsaid calculated distances between said autonomous mobile work system andsaid first and second base stations.

Another aspect of the disclosed technology relates to a method ofdetermining the location of an autonomous mobile work system comprising:providing a first and second variable reflectivity base station and anautonomous mobile work device, wherein said autonomous mobile worksystem is configured to calculate the distance between said base stationand said autonomous mobile work system; obtaining the distance betweensaid autonomous mobile work system and each of said first and secondbase stations; and calculating the location of said autonomous mobilework system using said calculated distances between said autonomousmobile work system and said first and second base stations.

Another aspect of the disclosed technology relates to a method ofdetermining the location of an autonomous mobile work system comprising:calculating the location of said autonomous mobile work system using acalculated distance between said autonomous mobile work system and afirst variable reflectivity base station and a calculated distancebetween said autonomous mobile work system and a second variablereflectivity base station.

Another aspect of the disclosed technology relates to a method ofdetermining the location of an autonomous mobile robot systemcomprising: using reflectivity to calculate the location of saidautonomous mobile robot system.

These and further features of the disclosed technology will be apparentwith reference to the following description and attached drawings. Inthe description and drawings, particular embodiments or aspects of thedisclosed technology have been disclosed in detail as being indicativeof some of the ways in which the principles of the disclosed technologymay be employed, but it is understood that the disclosed technology isnot limited correspondingly in scope. Rather, the disclosed technologyincludes all changes, modifications and equivalents coming within thespirit and terms of the claims appended thereto.

Features that are described and/or illustrated with respect to oneembodiment may be used in the same way or in a similar way in one ormore other embodiments and/or in combination with or instead of thefeatures of the other embodiments.

It should be emphasized that the term “comprises/comprising” when usedin this specification is taken to specify the presence of statedfeatures, integers, steps or components but does not preclude thepresence or addition of one or more other features, integers, steps,components or groups thereof.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

These and other features of the disclosed technology, and theiradvantages, are illustrated specifically in embodiments of the disclosedtechnology now to be described, by way of example, with reference to theaccompanying diagrammatic drawings, in which:

FIG. 1 is a flow chart representing aspects of an exemplary method fordetermining the distance between the variable reflectors and the mobilework system in accordance with one exemplary embodiment;

FIG. 2 and FIG. 3 are diagrammatic representations of the system in afirst state with equal reflection, a second state where the reflectionof one reflector has changed between a first and a second state, a thirdstate where the first reflector has returned to its original state and afourth state where a second reflector has changed to a differentreflective state;

FIG. 4 is a diagrammatic illustration of an exemplary system withmultiple reflective states for each variable reflector;

FIG. 5 is a diagrammatic illustration showing that variable reflectorsmay be moved by the user or by the mobile work system to allow for largecoverage areas in accordance with one exemplary embodiment;

FIG. 6 is a diagrammatic illustration showing swarms of autonomousmobile work devices, each with variable reflectors and reflectionsensors with optional non autonomous variable reflectors in accordancewith one exemplary embodiment;

FIG. 7 is a diagrammatic illustration of an exemplary mobile work deviceand an exemplary variable reflector base station in accordance with oneexemplary embodiment;

FIG. 8 is a diagrammatic illustration showing one system for creating avariable radar reflector in accordance with one exemplary embodiment;

FIG. 9 is a diagrammatic illustration showing an optical variablereflector based upon bi-stable display technology such as bi-stablecholesteric LCD technology in accordance with one exemplary embodiment;

FIG. 10 is a diagrammatic illustration showing calibration of the mobilerobot location using a known location tag and onboard tag sensor with acombination of cameras, radar systems or both in accordance with oneexemplary embodiment.

It should be noted that all the drawings are diagrammatic and not drawnto scale. Relative dimensions and proportions of parts of these figureshave been shown exaggerated or reduced in size for the sake of clarityand convenience in the drawings. The same reference numbers aregenerally used to refer to corresponding or similar features in thedifferent embodiments. Accordingly, the drawing(s) and description areto be regarded as illustrative in nature and not as restrictive.

DETAILED DESCRIPTION OF EMBODIMENTS

Aspects of the disclosed technology relate to a method and system forlocalizing and confining an autonomous mobile work system or systems forperforming work in a user defined space is disclosed. In one embodiment,the system includes two or more variable reflective base stations atfirst and second locations that can modify their optical orelectromagnetic reflectivity based upon either an external command viawired or wireless communications interface, or automatically on aregular or asynchronous time schedule under programmed or user settablecontrol. The system also includes one or more autonomous mobile worksystems capable of sensing the state of the variable reflectance basestations via sensors such as electromagnetic or optical sensors capableof measuring distance to the reflective base stations.

The autonomous mobile work systems may have variable reflectivitysystems, cameras, GPS and other sensors capable of augmenting thedetermination of the work system's position. Additionally, the variablereflectivity base stations may contain sensors for measuring thedistance from the base stations to the autonomous mobile work system andthe reflectivity of the autonomous mobile work system. The autonomousmobile work system also may itself have a system variable reflectance.Prior to measuring any combinations of distance and reflectivity, thesystem is taught or autonomously learns the location of the reflectivebase stations via user or sensor input, earlier obtained locationinformation or use of an automatic secondary positioning system such asa satellite based system or other local positioning system (globalpositioning system or GPS). A first reflective state and distance orangle to at least one of the base stations are measured by thereflective distance or angle and reflectivity sensors on the autonomousmobile work system. If this measurement is the initial measurement, itmay be considered a background reflectivity and distance or anglemeasurement. Then a reflectivity change command or a fixed orasynchronous time signal is provided to at least one of the basestations which changes to a second reflectivity state in response to thecommand or signal. A measurement of the distance or angle andreflectance of the same, first reflective base station is then takenmeasured again. A difference of reflectivity between the first (orbackground) and second reflectivity states of the first variablereflectance base station is calculated and measured via the systemcomputational resources or determined by analog calculation viaelectrical circuits of the electronic sensor system or systems. Thisdifference is stored in a system memory.

The difference between these reflectivity measurements is used toidentify the base station which was commanded to change reflectance andto verify that the first base station actually changed reflectance inresponse to the command or signal. Then after a second command or asecond fixed or asynchronous time signal is provided to the first basestations it transitions to a different reflectivity state from thesecond state and the reflectivity of the first base station and distancebetween the first base station and the autonomous mobile work system areonce again measured and stored in a memory system. The reflector couldalso be changing reflectivity at a constant or asynchronous rateindependent of control signal. A comparison of the second reflectivestate and the different reflective state are calculated and confidenceis gained that the base station of is identified.

This process is repeated as necessary so that the mobile work system cangain confidence it has identified the distance to the location of thefirst reflective base station which was commanded to changereflectivity. In another instance, the rate of change of thereflectivity could be known or a modulated asynchronous change inreflectivity could be identifiable in a reflectivity measurement. Insome instances, measurements of only two reflective states and distancesare necessary to identify and determine range to a particular basestation. The identification and distance determination process is thenrepeated for at least one other reflective base station placed at asecond known location. Then taking the stored data from the locations ofthe base stations, measurements and estimates of the distance betweenthe measured base stations and the autonomous mobile work system, thelocation of the mobile work device can be calculated using a number ofdifferent methods of position determination including, but not limitedto, triangulation, multi-lateration or trilateration. The mobile worksystem may use the calculated location information about mobile workdevice position, the position of the variably reflective base stationsand if necessary, in conjunction with other sensors such as GPS, deadreckoning, and on board vision systems to localize, correct positioninformation, map, move the autonomous mobile work system and bound themovement of the autonomous mobile work system within a user taughtboundary to perform work such as mowing or cleaning an area.Additionally, the system may include any of the well known physicalboundary systems in addition to or in place of user defined boundaries.This system also can be used in conjunction with a teaching method toteach the autonomous mobile work system a coverage area for theautonomous mobile work system based upon location measurements takenduring the commands input by a user. Also disclosed is a unified workapparatus comprised of at least one autonomous mobile work system andtwo or more variable reflective base stations.

Aspects of the disclosed technology recognize that conventional systemshave proven over time to be too unreliable, expensive or complex for usein consumer products. Moreover, aspects of the disclosed technologyrecognize that there has been a long felt need for local navigationsystems which are simple to use, reliable and very low cost for use inconfining and locating autonomous mobile work systems. The significantprocessing power (both computational in MIPS and electrical in watts)and the complex electronics and software required for optical visionbased location systems and for radio location systems are barriers tothe success of these systems.

Additionally, aspects of the disclosed technology recognize that thereare a number of factors which degrade satellite based GPS signals whichare outside the control of the system user. These include, but are notlimited to, atmospheric conditions, multipath reflections, receiverclock errors, orbital errors, satellite geometry and artificialdegradation of the satellite signals. Thus, there are many times,situations and environments where satellite based positioning systemsare not adequate for sub-meter level autonomous mobile work systempositioning and location. Instead, a high performing, low costautonomous mobile work system localization system needs a simpler morereliable location system. Incidentally, low cost commercially availablecomponents that allow for GPS independent confinement and localizationjust now are becoming available.

For instance, many low-cost radar systems are now becoming widelyavailable. Examples of these systems include ultra wide band andautomotive gigahertz bandwidth radar systems. Additionally, with therise of stealth radar avoidance technology and the ability to vary orcontrol the radar cross section of an object is possible either byelectromechanical or electronic means, it has become easier and lowercost to vary the radar cross section of an object. Furthermore, one canemploy, for example, radar reflectors and enhancers as currentlydeployed in marine applications, which could be used to modify the radarcross section of a variable radar reflector. By using these technologiesone can design a triangulation, multi-lateration or trilateration systemfor an autonomous mobile work system whereby the system can identifyvariable location base stations via wireless commands to change thereflectivity of those base stations.

In the field of consumer based, area-confined autonomous mobile worksystems, it is possible for the system to have multiple separate basestations which can have system controlled variable reflectivity. Incontrast, many typical autonomous mobile work systems require locationsystems which are much more expensive and are independent. Thisrequirement leads most autonomous mobile work system designers away fromsystems that have physically separate system parts which change aphysical characteristic based upon timing or a command. However, theautonomous mobile work system disclosed herein requires only slowlymoving mobile work systems that have a time to acquire reflectivity anddistance or angle measurements from independent variable reflectancebase stations with reflectance being controlled by the system itself andthe location of the base stations being known to the system.

In the past several systems exist that have higher power and expensiveactive RFID tags or very short range passive RFID tags. These systemsare non-optimal due to customer maintenance needs, limited range ofoperation and higher cost transmitter and receiver electronics.Moreover, range limitations of short range RFID tags make themnon-optimal for use in location systems.

The system disclosed herein could be used for automated mowing,cleaning, or monitoring of an area or for locating people or objectswithin that area. One of the key advantages of this system is that thesystem can self-identify the reflectors so that system cost,computational power of location determination can also be greatlyreduced. The amount of system memory can be greatly reduced and noexternal computing such as cloud computing would be required. Unlikecomplex vision systems, databases of known objects or textures is notrequired since the reflectors are controlled and have a known locationin relationship to the environment. Furthermore, this system eliminatesthe need for complex cloud computing infrastructures and reliance uponmultiple computer systems for calculating position as used in today'sautonomous vehicle systems. The sampling time, computational time andnumber of calculation sequences can be kept very low, thereby freeingcomputational resources for other tasks such as safety, security, userinterfaces and mapping algorithms. A surprising result is that low costbut high quality radar or optical sensors are capable of locating anautonomous mobile work system can be obtained by the simple concept ofcontrolling, identifying and determining distances to external variablereflectors via simple low cost sensing and control of reflectance with aminimum of computational power.

Moreover, the system is readily extensible, and is not limited to fixedbase stations. The system can be used with multiple user defined orsystem learned locations of fixed reflectance points to augment systemaccuracy and precision. For example a user can identify a fixed objectin the autonomous mobile work system's field of sensor detection anglewhich could eliminate one of the variable reflectors. This identifiedobject could also be a special unchanging passive reflector, visiblefiducial or object of specific, shape, color or spectral reflectivityresponse. Additionally, the system can allow for easy movement of thereflectors either by the autonomous mobile work system itself or by anexternal user. Also, as many variable reflectors as necessary can beadded to the system to allow for larger and larger coverage areas andmultiple charging stations can be added, as can multiple mobile worksystems. Multiple autonomous mobile work systems with variablereflectors can be added, moved by the system and used to increaseaccuracy and extend system range to create a swarm of mobile worksystems, and variable reflective base stations.

The implementations described herein solves the above problems andlimitations of corrected and non-corrected global positioning systems,dead reckoning, electromagnetic dog-wires, and complex vision systems asused mobile work system location in part by using off the shelf opticalcameras or very low cost radar systems in conjunction with independentbase stations having system controlled variable reflectivity. By meansof the system either receiving or determining the location of these basestations via vision systems, local or global positioning sensors, thesystem is able to calculate the position of a mobile work system with orwithout user input. The sensors for the location system could be locatedon the mobile work system or on one or more of the base stations.Additionally, the reflective base stations could be included on one ormore mobile work systems or all systems could have variable reflectors.

The autonomous mobile work system, at least in part, comprises one ormore autonomously movable work systems and at least two stations withvariable reflectors. The work system could be an autonomous mobilecleaning system or an autonomous mobile work system for security andsurveillance, mowing, grass collection, leaf cleaning or the like. Thesystem contains one or more distance sensing systems such as a gigahertzradar system, ultrasound system or ultra wide band radar system, orstereo camera system for measurement of distance. The variablereflectors could be optical reflectors such as standard reflectiveliquid crystal panels, bi-stable liquid crystal panels such ascholesteric liquid crystals, magnetically changed variable reflectors,curved reflective panels that transition from straight to curved,diffractive variable diffractive optics, mechanically changed in area orone of many other mechanisms for changing the size, shape, beamsteering, or gathering of light to increase their reflectivity. Thesystem could rely upon sunlight, ambient light or system providedillumination to allow stereo camera or cameras to measure the distancebetween the reflector and other parts of the system. Additionally laserillumination of the reflectors could be used. This reflectivity isvaried upon command of the system based upon a fixed time signal,external mobile work system command or asynchronous time signal. By useof this system the positions of the reflectors can be used to calculatethe angle between the variable reflector and the mobile work system. Thechange in reflectance may be spatial or directional. For example thecurvature of a surface, pattern of reflectance or direction of areflector could be changed to cause a change in reflectance. Diffractiveor resonant techniques could also be used to change the amount of lightreflected to the sensor. A resonant laser cavity or an adjustablemulti-plate fabry-perot interferometric diffractive reflector could beused wherein the plate separation could be modified to create a variablereflector. The curvature of a mirror could be changed by capacitive,electrical or electromechanical means to alter reflectivity of areflector. Physical orientation of a reflector could be used, such as bya reflector being moved by a motor or a reflective surface being coveredby a shutter. Also the aperture of the reflective surface could bevaried in order to change the reflectance of the system.

In some embodiments, the reflectivity of the base stations could have aunique time dependent variation of reflectivity that is detectable viathe autonomous mobile work station's reflectivity sensors. The frequencyof variation in reflectivity could be unique for each base station,allowing identification of a particular base station as the system knowsor was taught the reflectivity of every base station present in thesystem. Well known modulation and frequency detection algorithms andcircuits could be used to detect the variation of the reflectivity andto calculate the variation of a particular base station's frequency.Additionally the variation of the base station reflectivity could bemodulated with an encoded signal which could be detected and used toidentify it as a particular base station. The sensor system would becapable of de-modulating the information from the measured reflectivityof the system. Being a passive reflector has the added benefit ofkeeping the system cost and power low while still having the ability toindicate the identity of individual base stations for use inlocalization of autonomous mobile work systems.

In another embodiment, radar reflectors can be made to have a variableradar reflectance cross section by the cross section being physicallymodified or electromagnetically charged and discharged. In this instanceone or more low cost radar systems can be used to detect the distance orangle and reflectivity of the mobile work system or base station withvariable radar reflectance cross section. The speed of the radar crosssection variation could be from slow statically changing states up tohigh frequencies. The advantage of using radar system is their abilityto measure through obstructions such as fences and walls, and theirability to see through dust, dirt and many weather conditions.

An included optical system may be used with visual user identificationalgorithms for system theft deterrence, as theft of autonomous mobilework systems remains a problem. The user could program the system torecognize a fixed feature of the property and thereby require the systemto find and recognize that fixed feature of the work area beforeallowing work operations to be performed again by the mobile worksystem. Also, any included radar or vision system can have dual use forlocation of obstacles, obstacle avoidance, or identification of movingobjects.

One aspect of the disclosed technology relates to a method wherein afirst mobile work device (e.g., a robotic lawn mower) and at least oneor more reflective boundary stations are located within an area (e.g., auser-defined or predefined area, such as a yard). The method furtherincludes providing the location of the variable reflectors placed in awork area are provided to the system via user input, internal orexternal location system. The method includes completing a calibrationsequence allowing the system to identify an orientation and location ofthe variable reflectors. The method also includes taking a background orfirst measurement of at least a first and possibly one or moreadditional reflectors. The method also includes changing a firstvariable reflector's reflectance state via timing signal or commandsignal. Measuring a distance or an angle and a reflectance between themobile works system and at least one variable reflective base station istaken to the first reflector.

Next, calculating a difference in reflectance of the background and thesecond measurement. The method includes changing the first variablereflector's reflectance state again and again measuring this station'sreflectivity, and angle or distance. Then the method further includescomparing the first measurement to the second measurement and ifnecessary to the background measurement. Storing the distance or anglein memory. If necessary, the method may include commanding one or moreof the variable reflectors to have a third, or even fourth, fifth andmore, reflective state or a first (original) reflective state and thenmeasuring the distance or angle and reflectivity and these subsequentmeasurements are placed in a system memory.

The method includes the steps of repeating the sequence of changing andmeasuring and comparing as necessary until the mobile work system gainsconfidence the distance or angle to the first changed variable reflectoris determined. The method further includes repeating this sequence ofcommanding changes in reflectance and repeating measurements with anyadditional variable reflective base stations as necessary to gainconfidence in the mobile work system position and storing this data in amemory.

In some instances the method includes identifying or providing anindication of a fixed reflective object such as a house, tree or otherstationary object and using this in place of one of the variablereflectance base stations. The method also includes a method ofmeasuring or receiving a distance between at least one variablereflector and an identified fixed object. The method also includescommanding the autonomous mobile work system to move within a closeproximity of the fixed object location. A distance correction ismeasured to the fixed object location. A second measurement of distanceor angle and reflectivity is taken from the fixed object to a variablereflectance base station. This is used as a background measurement.

The system commands a change in reflectivity of the variable reflectancebase station and another measurement of the variable base station'sangle or distance and reflectivity is taken. The location of thevariable base station also is known, acquired or input by the user. Alsothe location of the fixed object is known, learned or input by the user.The mobile work system moves to a third known position as input orlearned by the system. Then the method further includes again repeatingthe described sequence of measurement of distance or angle to andreflectivity of the variable reflectance base station are taken. Anorientation is calculated to the fixed object in relationship to the newposition of the mobile work system and the fixed object are completed.The method includes commanding the mobile works system to turn an angleat which the distance measurement and reflectivity sensors are capableof measuring the reflectivity of and distance or angle to the fixedobject. This method is used to verify, calibrate and use the combinationof at least one variable reflectance base station with a fixed object totrack position and construct a work area map which is stored in systemmemory.

Furthermore, the method includes determining and mapping location, andorientation of any of the number of variable reflective base stations oradditional mobile work system with variable reflectors with respect tothe mobile work system; commanding a change of angle to place the systemsensor in a position to measure angle or distance and reflectivity of atleast one variable reflective base station or additional mobile worksystem with a variable reflector based upon a calculation of orientationand location obtained by comparing the mobile work system's currentlocation to a map contained in a system memory which contains theposition of the variable reflective mobile base station or stations. Themethod of map creation also includes inputting or determining thelocation of the variable reflective base stations, mobile work systemand a system working boarder determined from user input.

The system and method allows for user input of obstructions andpositions where a mobile work system may not detect a variable basestation. The system then calculates lines of sight from each potentialposition of the variable reflective mobile base station and provides anindication where the mobile work system cannot obtain a measurement ofdistance or angle and reflection. Then map areas are marked in memorywherein the mobile work system cannot expect to obtain a measurement ofangle or distance. As the mobile work system traverses the work area, itcompares its location to the map and determines if it is in a keep outarea. In accordance with an exemplary embodiment, the method can furtherinclude using a combination dead reckoning, GPS sensors or opticalsensors to provide a path to traverse so the system can exit the keepout area.

If necessary, the method may include commanding the orientation of themobile work system to change in order to correctly discover and measureone or more of the variable reflectance base stations. This wouldrequire a sequence of first turning the mobile work system or the sensoron the mobile work system to an orientation, attempting a sequence ofidentifying the first variable reflector's changing reflectance and ifthe reflector is not found, again changing the orientation of thereflector and attempting location through the above disclosedmeasurement sequence. Additionally a map, a history of orientations anda matrix transform may be performed to re-orient the mobile work systemto more easily acquire measurements of one or more of the variablereflectance stations. The system can determine angle via at least one ofan onboard compass, a gyroscope or accelerometer, dead reckoning,environmental pattern observation, comparison and mapping via videocamera or wheel odometers.

If the measurement sensor's field of view allows, the measurement ofchanged reflectance and distance can be done for at least a secondreflector simultaneously and the sequence of measuring as describedabove can be completed for the second variable reflector. If it cannotbe done simultaneously, the mobile work system, if necessary can changeits physical sensor orientation in order to locate and measure a secondvariable reflector's reflectance, distance or angle and the describedmeasurements of the second reflector are taken. The system's currentknowledge of its location in relation to a stored map can be used toaugment orientation selection and minimize turning angle in order toobtain a direction for sensing of at least a second variable reflector.The second reflector changes its reflectance based upon a time signal ora command signal. The measurement of the second variable reflector'sreflectance and distance or angle from the second variable reflector tothe mobile work system is measured again.

Measurement sensors for the mobile work system can be of the upwardviewing stereo camera type with 360 degree reflector for 360 degreeviewing. This allows the mobile work system to identify the reflectivebase stations all at one time regardless of the system and to identifyany obstructions that may be in the line of site of one or more of thereflective base stations. It also allows for 360 degree object detectionand viewing. Additionally, the radar sensor may be able to sense in 360degree sensing angle via either specially designed antennas, or rotatingradar sensor. Or the radar may have a fixed direction and the autonomousmobile work system may rotate to accommodate radar sensing.

After a complete set of distances or angles from the mobile work systemto the variable reflectors are taken, a location of the mobile worksystem is calculated. Methods such as triangulation, multi-lateration ortrilateration are used to complete the calculation of this distance.This sequence can be repeated as necessary to map, move or locate theautonomous mobile works station. Methods of filtering position,estimates of position and path planning can include algorithms such asdigital signal processing filters, FIR filters, IIR filters, Kalmanfilters or other similar methods. Additionally statistical methods canbe applied to the estimates of position to give a confidence that thedetermined location is at least within an acceptable error of theexpected position. Furthermore, well known curve fitting algorithms canbe employed to plan a path between at least a first and a second maplocation at which the system can determine using the disclosed variablereflectance location method. Curve fitting techniques include best fitvia interpolation, smoothing, regression analysis, or statisticalinterference. Also paths between boundaries can be mapped viaextrapolation or algebraic solutions to predicted curve fits. The errorbetween curve fit and measurement of location can be used to develop asystem model of the autonomous mobile work system's speed andorientation for creating adaptive filters and filter parameters forKalman filters or particle filters. Furthermore a probabilitydistribution fitting algorithms can be used to estimate the probabilitythat the system is working obtaining accurate position and orientationsbased upon commanded velocity and orientation.

The mobile work system then may move to other locations and againdetermine its location relative to the variable reflectors.Additionally, the variable reflective systems and mobile work system orsystems may contain GPS systems, RTK-GPS system or other errorcorrecting GPS system to allow for a secondary accurate positioning ofthe mobile work system for obtaining or improving position informationof the reflective work systems and the mobile work system. All of theabove listed systems, mobile work system and variable reflector systemsmay contain wireless or wired communications links to share positioninformation and to provide data to position correction algorithms. Thesecommunications systems may be point to point, broadcast, full or halfduplex. Each mobile work system, variable reflectance station andcharger may have a unique identification code.

They system may also contain wireless encryption data transfer systemsto prevent unauthorized access to the communications between the systemparts. Correction algorithms such as real time kinematics ordifferential GPS could be used to correct the location information.Moreover, an external command system may enable commands to change areflectivity of any of the system's variable reflective base stations,add a variable base station, change the identification number associatedwith a variable reflectivity base station via user command orpreprogrammed list of associations between base station andidentification numbers.

To teach the system a work boundary, the system may comprise a removablesensor system which can be removed from the mobile work system. Thesensor system has at least one of a, position location, ranging,reflectance or angle measuring sensor for measuring the distance,reflectivity and angle to the variable reflectors. The removable sensorsystem may contain a GPS system for improving the location calculationsof the sensor for perimeter location determination. Additionally thesensor may have means for communicating with a smart phone. Theremovable system may contain an inertial measurement unit to detectmotion for correction of location. The smart phone's GPS, cellular,Wi-Fi, wireless and location systems and algorithms may be used inconjunction with the sensor's own capabilities to correct or improve theboundary location measurements. Also the smart phone may have anapplication to store the location information, use allow the user toview the final boundary, and modify it, transfer it to a secondarycomputer for storage and modification and return it to the system as acompleted work boundary. The same methods may be used to teach themobile work system areas in which not to enter on the interior of theboundary or areas where the system may travel but not complete work togo between multiple work areas.

Once the removable sensor system is detached from the mobile worksystem, the user can proceed to move about the perimeter of the workarea. The user can provide an indication via user command to inform thesystem the path being traveled is part of the boundary or to tell thesystem that it is not part of the boundary. The system, in the same wayas above, takes measurements of location, stores locations on theperimeter and maps a boundary of the work area. The system thenconstructs a work perimeter based upon the tracking of the removablesensor. The system can command the user to pause, point the sensortoward the variable reflectors, and then proceed as necessary toaccurately obtain location data or to correct a GPS sensor embedded inthe removable sensor system. Upon completion, the user can command thesystem to close the work boundary and return the unit to the mobile worksystem.

The positioning sensor system may also employ filtering software toallow smoothing correction of the stored location methods and may have aline fitting algorithm to create a closed path around the autonomousmobile work system or station's indented work area or areas. Theremovable sensor system may have a memory for storing the boundary andmap of the autonomous mobile work system's intended work areas, keep outareas and non-work travel areas. This information may be transferred toa secondary computing device for correction, augmentation, mapping, postfilter processing or verification. This information may be transferredto secondary computing systems via removable flash memory, wireless,serial link, I2C, SPI or CAN bus other common communications protocol.Additionally, the system may use the included variable reflectivesystems to encode messages or transfer information between theautonomous mobile work systems and variable reflectance base stations.

Also, the user may connect the system to a separate computer or mobilephone for later storage, review and modification of the boundaryinformation. This information map can be provided via wireless link,Wi-Fi, Ethernet, Bluetooth, USB memory stick or flash memory card to thesystem for commanding the mobile work system's boundary and movementpatterns.

Each of the variable reflectivity systems may comprise one or more ofthe following a GPS system, a wireless transmitter, wireless receiver,wired transmitter and/or a wireless receiver. Also the variablereflectors can contain electronics, motors, variable reflectors,mechanics and optical systems suitable to change the reflectivity of thesystem. In one embodiment the system uses the GPS receiver to obtain thevariable reflectivity system's location.

In another embodiment the mobile work systems can contain at least oneGPS sensor which is used to map and verify the location of the variablereflectance base stations. In at least this instance, the variablereflective base station is moved to within a close proximity to avariable reflective base station. Then the GPS location of the mobilework system is then indicated as the non-corrected variable reflectancebase station's location, a distance from the mobile work system andvariable base station are measured or entered and an orientation of themobile work system is recorded using orientation sensors included on themobile work system and stored in a memory. The mobile work system ismoved to a second location proximate to the variable reflectancestation, a second GPS reading and a measurement of distance to andorientation of the variable reflectance base station is recorded in amemory. Then using standard location mathematics as highlighted above,the location of the variable reflectance base station is determined andrecorded in a memory. The mobile work system repeats this method in toobtain the location of additional variable reflectance base stations.Moreover, the location of the variable reflectance base stations mayhave been known prior to this measurement, allowing for correction ofthe autonomous mobile work system's indication of the GPS indication ofposition.

In another embodiment, a user could connect a mobile phone to each basesystem in turn and command it to obtain GPS location information fromthe phone. This connection could be physical via audio output jack, USBconnection, serial connection or wireless connection via Bluetooth,Zigbee, WiFi or other similar wireless link. The system would use a GPSreceiver or receivers to correct the location of zone variablereflectance base systems in conjunction with a GPS contained withinanother base system at a fixed distance from the first base station or aGPS on the mobile work unit or a fixed external base station ascontacted via the internet.

Additionally, the mobile work system would include at least some of thefollowing systems, an electrical drive system, motors, gearing gears,control module, radar sensor, ultrasound sensors, Wi-Fi, wireless links,can bus, mod bus, lin bus, rs-232 serial link or similar communicationslinks. Also the system could include inertial measurement units,compasses, accelerometers, gyroscopes, odometers, stereo cameras, radarand the like for creating multi sensor algorithms for correction of thelocation information obtained by the variable reflectance locationsystem. The mobile work system may also contain a battery and powersystem comprising at least one of a battery, fuel cell, capacitor orother commonly known storage element.

In another embodiment, the autonomous mobile work system would contain amechanism to pick up each of the reflective base stations in turn ortogether, move them to another location, drop them and re-calibrate thelocation of each of these variable reflective base stations. Calibrationof position information could be completed with the GPS based methoddescribed above, through the use of multiple mobile work systems orthrough user input. This would allow a larger coverage area and a morerobust location system that could account for complex geometries andsystems that allow for coverage around a home or around obstructions ina work area.

In another embodiment the system will have autonomous multiple mobilework systems, which each have variable reflectors, wireless links, drivesystems, computing systems, distance and reflectance measurement systemsand memory systems, mapping and path planning systems. Additionally, thesystem may have more variable reflective base stations. These mobilework systems can each measure the distance and location to the otherautonomous work systems and to the variable reflectance base stations.When the number of work systems is greater than two, the mobile worksystems can be used to calculate the positions of all the mobile worksystems. Using a similar position location algorithm the location ofeach mobile work system can be calculated. At least two of the mobilework systems remain fixed at known locations and the third location iscalculated. Then either the first or second work system can be movedwhile the third workstation is able to be moved and then the position ofthe third work system is calculated.

With the addition of variable reflectance base stations, they can beused as an initial positioning location anchors to provide a baselinecalculation of at least two of the mobile work system for calculatingthe position of at least a third mobile work system. Moreover anidentified fixed object could be used as another means for correct thelocation of each autonomous mobile work system. This allows round-robinmovement of the mobile work systems to increase the coverage area to anunlimited size or a size only limited by battery power of the system.

Additionally, the mobile systems could have charging apparatus fortransfer of power from at least one of a first mobile work system to atleast a second mobile work system to allow for larger coverage area. Inthis instance, a first mobile work system is charged via a fixed chargestation which may be a variable reflective base station. Because theenergy required to move the autonomous mobile work systems is lower thanthe power used during the work process such as mowing, blowing,vacuuming or the like, the energy stored in the batteries of a firstmobile work system could be transferred to at least a second mobile worksystem.

In another embodiment, one of the reflective base stations could alsoserve as a charging station. The charging station could be connected toa power outlet or could have an alternative energy source such as wind,bio-fuel cell fueled by grass clippings or plant debris or solar power.This charging station could ether be larger than the mobile work systemor smaller. In the instance the charging system is smaller than themobile work system; the mobile work system could lift and attach thecharging station to the mobile work system or stations allowing chargingof the batteries.

Moreover, the charging stations can be configured to accommodateswappable batteries, wherein the battery packs could be exchanged forcharging and alternately working. A first battery pack can be chargingwhile a second battery pack can be picked up by the autonomous mobilework system. The mobile work system would contain a temporary chargestorage system derived from one of an indicative coil, a capacitor, afuel cell or a battery. This storage system can be charged by theprimary batteries while attached to the mobile work system.

The system first charges the secondary power source with an adequatepower level to charge move the autonomous mobile work system without theprimary batteries. The charging station is places within the definedwork area of the autonomous mobile work system. When the voltage orcapacity of the first battery pack reaches a preset level, theautonomous mobile work system uses its knowledge of the location of thecharging station as indicated by the user, or as found via a variablereflector attached to the charging station through scanning theenvironment for commanded changes in reflectivity. Once found the mobilework system plans a path to the charging station, and a command isprovided to the mobile work system to travel to an open charging port ofthe charging station. The mobile work system's primary batteries areplaced into contact with a first charging port on the charging stationand released from the mobile work system. Then the autonomous mobileworks station would move to a second battery back being in a chargedstate via power stored in at least the secondary power storage element.Then the autonomous mobile work system proceeds to load the at leastsecond set of charged primary power cells into the autonomous mobilework system. The autonomous mobile work system proceeds to complete thecommanded work task in the defined work areas as necessary under thepower of the second set of primary power cells.

In another embodiment, the base station can be smaller than theautonomous mobile work system and could picked-up for connection of themobile work system. Typically most charging base stations are deviceswhich the autonomous mobile work system docs with. However, in order tosave overall systems cost, the base charging station can be smaller thanthe autonomous mobile work system and could be picked up by theautonomous mobile work system. The autonomous mobile work system couldthen connect the power connectors to the autonomous mobile work systemfor charging of the system batteries. This same charging system could beused to charge re-chargeable batteries in the other non-power connectedvariable reflector stations. They could be moved to locations within theyard or could move under their own power via an independent drivesystem.

In another embodiment, the reflective base stations and the mobile worksystem all can include reflection and distance sensors and variablereflectors. In this way the combination could verify location of anumber of mobile base stations and variable reflectivity base stations.These base stations and mobile work systems could be moved or could movein order to increase the coverage area of the work systems.

In another embodiment, a combination of both optical sensors and radarranging systems are used together to calculate the location of themobile work system or systems. Additionally secondary inertialmeasurement units could be used to augment the position calculation fromthe combination of the optical sensors ad radar ranging sensors. Theoptical sensors could be a camera, a stereo camera, or a polarity ofcameras capable of measuring distance, shape, size, color, spectralreflection content or a combination of these measurements. The mobilework system can include a camera, a stereo camera or a plurality ofcameras capable of locating one or more of the variable reflective basestations. The reflective work system could vary reflectance by intensityof light or by reflected spectral response.

The location of the base station can be completed using, for example,visual pattern and object recognition means. Upon location of the basestation, the mobile work system would then orient itself so that a radarsensor is capable of sending a first pulse to at least one of thevariable reflective base stations. An orientation of the mobile worksystem is saved in memory. A first command is sent from the mobile worksystem to the base station to command a first reflectance state of themobile base station. A first response from the first variablereflectance base station is sent to the mobile work system. Then a firstmeasurement of the base station reflection and distance is taken andstored. Next, via wireless link a command is sent to the first variablereflectance station. In response to this command the station changes itsradar or cross section to a second radar cross section. A radiocommunications response is sent from the base station to the mobile worksystem indicating that the reflectance has changed. The mobile worksystem receives the command and then this mobile work system takes asecond radar reflectance measurement is taken, stored and compared tothe first radar reflection measurement. This set of measurements is usedto for verifying distance from the mobile work system to the basestation and a change in reflectivity, the variable reflectance stationis commanded to change the reflectance to the original state. Again anacknowledgment message is sent from the base station to the mobile worksystem and in response a measurement of reflectance and distance to thebase station is taken. This measurement increases the confidence thatthe correct variable base station is selected and the distance to theproper base station is measured. Each base station has a uniqueidentification address that is encoded into the wireless messages.

In another embodiment, the unique radar signature (spectral frequencyresponse) or the unique visual appearance of the reflector allows thesystem to verify that the correct base station is activated, measuredand identified. In this instance the radio base station only musttransmit a radio message with a unique address for the variablereflectance base station and the variable reflective base station onlyrequires a radio receiver rather than having a receiver and atransmitter.

In another embodiment, the wireless link may be eliminated and replacedwith variable reflectors on the mobile autonomous mobile work system, avariable reflector on the base station, and one or more cameras on eachof the reflective base station and mobile work system, respectively. Asignal may be encoded or added to the variable reflectors in order totransfer messages between the system components.

In another embodiment, the system may be taught with a compass and userinput or GPS to know the orientation and direction of the variable basestations when the mobile work system is at a particular location. Theseorientations are then used to calculate mobile work system pose relativeto the variable reflectors. Then before each measurement of a particularbase station calculates the proper orientation and turns the mobile worksystem to that orientation in order to obtain the measurement ofreflectivity and distance to the variable reflectance base stations.

Also disclosed is a unified work apparatus comprised of at least oneautonomous mobile work system and two or more variable reflective basestations.

In accordance with on aspect of the disclosed technology, an autonomousmobile work system for performing work in a user-selected area caninclude one or more of the following elements without departing from thescope of the disclosed technology.

a. A mobile work device that includes one or more of the followingelements.

i. Motor drive system

ii. DC or brushless electrical motor

iii. Gearing system

iv. Four Wheels

v. Servo steering system

vi. Cutting, vacuuming, sweeping or cleaning system

vii. Power converters and dc-dc converters

viii. Multipoint wireless transceiver such as a IEEE 802.15.4 ExtendedRange Module

ix. Optical encoders

x. Visual odometer sensor

xi. Sensor board or boards including one or more of the followingelements.

1. Three axis accelerometer

2. Three axis Gyroscope

3. Three axis Magnetometer

4. Tilt sensor

5. Rain sensor

xii. User interface

1. Liquid Crystal Display

2. Control buttons

xiii. Enclosure

xiv. Frame

xv. Single board computer

xvi. Servo and Motor Control boards

xvii. Wi-Fi connection

xviii. Emergency stop button

xix. Bump sensor

xx. Radar Sensor

xxi. Stereo Vision system

xxii. Can Bus

xxiii. Serial Bus

xxiv. Ultrasound range sensors

xxv. Charging connections

b. At least one variable reflectivity base station including one or moreof the following elements.

i. A system controllable variable radar reflector

ii. A control board including an embedded computing system

iii. A power system for powering the base station

iv. A wireless receiver or wireless transmitter

v. A GPS receiver

vi. A GPS antenna

vii. A radar reflector with variable radar cross section

c. At least one charging base station including one or more of thefollowing elements.

i. Contactors for contacting mobile work station charging connections

ii. A control panel

iii. A Wi-Fi Receiver

iv. A Ethernet receiver

v. Multipoint wireless transceiver such as a IEEE 802.15.4 ExtendedRange

vi. A radar reflector with variable radar cross section

vii. A power system

viii. A charging system

ix. A housing for containing the electronics

x. A motor and mechanical linkage for moving the orientation of thevariable reflector from at least a first to at least a second ormultitude of reflectivity states.

In accordance with one exemplary embodiment, a method of determining thelocation of an autonomous mobile work system can include one or more ofthe following steps.

a. A user providing the location and orientation of a first variablereflective base station.

b. A user providing the location and orientation of a second variablereflective base station which is located at a different location thanthe first base station.

c. The autonomous mobile work system being at a third location,different than the first and second locations of the first and secondbase stations.

d. The autonomous mobile work system providing a command to the firstbase station to change its reflectivity.

e. The base station then changing its reflectivity in response to thecommand.

f. The autonomous mobile work system then measuring and storing thereflectivity of the first base station and distance from itself to thefirst base station.

g. The autonomous mobile work system then commanding a change in basestation reflectivity to a second reflectivity state.

h. The base station then changing its reflectivity in response to thecommand.

i. The autonomous mobile work system then again measuring and storingthe reflectivity of the first base station and distance from itself tothe first base station.

j. Then the mobile work station commanding a change in base stationreflectivity to a different reflectivity state (either the first or athird state).

k. The autonomous mobile work system then again measuring and storingthe reflectivity of the first base station and distance from itself tothe first base station.

l. Then the system computing system calculating a difference inreflectivity of the base station after each commanded reflectivitychange.

m. This method is repeated as necessary to verify the autonomous mobilework system's distance to the first base station.

n. The autonomous mobile work system's radar sensor is turned to thesecond orientation in a direction of the second mobile base station toallow measurement of the second base station's reflectivity andorientation.

o. The autonomous mobile work system proceeds to repeat theidentification of the second base station and measurement of distance tothe second base station.

p. The known locations of the first and second base stations and themeasured distances are used to calculate the position of the autonomousmobile work system.

q. The process is repeated as necessary to obtain the system locationwith a bounded area.

r. The method further including adding at least a third variablereflectance base station in a location different from the first andsecond base stations and the autonomous mobile work system usingcommanded changing reflectivity and measurements of distance to eitherincrease the autonomous mobile work system range or increase theaccuracy of the autonomous mobile work system's location calculations.

It will be appreciated that multiple mobile work devices can be employedwithout departing from the scope of the present invention.

In accordance with one exemplary embodiment, a system comprising aplurality of autonomous mobile work devices each having a systemcontrolled variable reflector can include one or more of the followingelements.

1. The variable reflectors being a radar reflector

a. The reflection being changed by charging and discharging a plate

b. The reflection being changed by moving or rotating a mechanicalsystem

c. The reflection being moved by magnetic means

2. The variable reflector, in the alternative, being a optical reflector

a. The reflector being a liquid crystal panel with multiple reflectancestates and patterns

b. The reflector having a variable aperture

c. The reflector having its reflectance changed by moving or rotating amechanical system

3. The variable reflector having a motor for moving the orientation ofthe reflector.

ii. The system further having at least one base station capable ofconnecting to a mobile work systems and charging the mobile worksystem's power source.

iii. The system having computing resources and wireless communicationssystem capable of commanding a reflectivity variation of at least one ofthe mobile work systems.

iv. The autonomous mobile work systems also having reflectivity anddistance sensors capable of measuring the reflectivity of a variablereflector and the distance from the mobile work system to a variablereflector.

v. The autonomous mobile work systems also having a wirelesscommunications system for exchanging data between the system components.

vi. The autonomous mobile work system having a unique identifying codecapable of uniquely identifying the mobile work system from all othersystem components

vii. The autonomous mobile work systems having a motor drive system formoving the mobile work system.

viii. The autonomous mobile work system having at least one rotationalservo for controlling the orientation of at least one direction wheel.

ix. The autonomous mobile work systems having at least one cuttingmechanism for cutting grass.

x. The autonomous mobile work system having a vacuum for collection ofgrass clippings, debris, leaves or other material located in a userdefined area.

xi. The autonomous mobile work systems also having a rechargeable powersource capable of providing power for driving system sensors,processors, and motor drives

xii. The mobile work systems further having global positioning sensorsfor determining position based upon global positioning system satellitesignals

xiii. The mobile work system also having tilt sensors, odometers,gyroscopic sensors and/or accelerometers for determination of systemmotion, orientation and augmentation of location information.

xiv. The system further having fixed location reflective base stationseach having a location either input by a user or determined by systemsensors and computations.

xv. The system further having multiple microcontrollers for sensorconditioning, motor control, and calculation of position based uponsensor data

xvi. The system having at least one control panel for defining workarea, controlling work schedules, determining system diagnostics andcontrolling system components and parameters

xvii. The system further having a wireless link enabling communicationwith the system via smart phone, PDA, computer or other wireless controldevice or mobile communication device.

xviii. The system further having storage means for storing computercode, work data, mapping and schedules

xix. The system also having computing resources and circuits forcalculating location, orientation, avoiding obstacles, determiningmovement paths and determining work boundaries

xx. The system further containing a camera for allowing identificationof a variable reflection base station

xxi. The system having a memory for storage of a map for multiplelocations for mowing.

In accordance with one exemplary embodiment a system for determininglocation having a variable mobile work device with variable reflector orvariable color can include one or more of the following elements.

1. A device or system for completing a task in a defined area such asmowing, cleaning or vacuuming, including one or more of the followingelements.

a. a mobile work system containing a variable reflector

b. the mobile work device further including one or more of the followingelements.

i. a drive system

ii. a computer control system

iii. a wireless communications link to a base station

iv. an energy storage system

v. tilt sensors

vi. a gyroscope sensor

vii. an accelerometer system

viii. a compass

ix. three or four wheels

x. at least one servo motor for positioning at least one directionalwheel

xi. a user control panel

xii. a system variable optical reflector having different reflectivecolor based upon a system command

xiii. a system variable radar reflector having a different radar crosssection based upon a system command

xiv. an ultrasound object detection system

xv. visual speed sensor

xvi. a charger interconnection system

xvii. a rain sensor

xviii. a work scheduling system

xix. a Bluetooth wireless link to a Bluetooth based controller

xx. a global positioning system signal receiver

xxi. a grass cutting blade system

xxii. an object bump sensor

xxiii. an ultra wide band radar object detection sensor.

xxiv. An electric wire confinement system

xxv. A magnetic wire confinement detection system

c. At least one remote reflection and distance sensor base stationincluding one or more of the following elements.

i. The reflection and distance sensor being capable of scanning theenvironment to identify the mobile work system to cover a defined workarea

ii. The sensor system comprising a servomotor for rotating thereflection and distance sensor by 360 degrees.

iii. The base station having a wireless link to communicate with themobile work station

iv. The base station having a controller programmed to control thesensor system, to analyze snapshots of the work area's reflectionprofile, and to communicate with the mobile work station

v. The base station controller commanding the mobile work station viathe wireless link to change to a first known color.

vi. The base station controller commanding the sensor to scan throughsufficient angle to identify items having the first commanded color.

vii. The base station controller upon identifying a remote object of thefirst commanded color and recording the scan angle of the first color,then commanding the mobile work station to stop moving and to change toa second color.

viii. The base station then using the scan angle information to scan thesame angle for the second color.

ix. If the second color is identified at the same location as the firstcolor, a distance measurement to the mobile work station is recorded.

x. The base station then commands the mobile work station to once againchange color to the first or another color.

xi. The system then identifies the mobile work station as having changedcolor in response to the command to change color and a second distancemeasurement is taken.

xii. The first base station having an shape or indication that allows itto be placed at the same angle as at least a second base station.

d. At least a second remote reflection and distance sensor base stationincluding one or more of the following elements.

i. The second remote base station having a memory location indicatingthe distance from the first base station.

ii. The second base station having a controller capable of controllingthe rotation angle of a reflection and distance sensor via a controlledservo motor.

iii. The second base station being placed at a second angular directionto the first base station.

iv. The first base station communicates with the second base station andmobile work system via wireless radio link.

v. The controllers each receive and send messages regarding sensorangles, mobile work station speed, color and distance information.

vi. The second base station controller calculates the proper scan angleof its sensor system based upon the known distance from the firstsensor, the scan angle of the first sensor and commands the sensor toturn to this angle.

vii. The second base station scans the mobile work station to verifycolor and measure distance from the second base station to the mobilework station.

viii. The second base station, upon identifying an object of theexpected color of the mobile work station, communicates that an objectof the correct color was detected at the calculated angle. Then adistance from the second base station may be calculated or measured.

ix. Then the system calculates the location of the mobile work stationin relationship to the fixed base stations and stores this location inan area map.

e. Based upon work requirements and coverage area, the system commands arotation angle and speed to the mobile works station in order tofacilitate completing work it the defined work area.

One aspect of the disclosed technology relates to a system for locationhaving a variable mobile work device with variable radar reflector.

In accordance with one exemplary embodiment, a system for determiningthe location of a mobile robot relative to two sensing elements with aknown location and separation includes one or more of the followingelements.

An autonomous mobile robot with a system controllable radar crosssection

A radar system with one or more radar sensors capable of measuring theradar cross section and distance to a mobile robot having a knownseparation distance between the sensor and a fixed location or betweenthe sensors and known location of every sensor

A wireless communications system which can exchange data and commandsbetween the radar sensor or sensors and the mobile robot, each of whichcontaining a radio transceiver.

A microcontroller or combination of microcontrollers working together asa microcontroller system programmed to send control commands andreceived data from to each of the radar system and the mobile robot

The microcontroller system being programmed to send a control signal tothe mobile robot to stop moving and to continuously vary the reflectanceof the mobile robot

The microcontroller system being programmed to read the data from theradar system and verify the distance or angle to the mobile robot byidentifying the time variation in the reflected robot sensor.

The microcontroller system using the distance or angle information todetermine the location of the mobile robot

The mobile robot having additional sensors including accelerometers,gyroscopes, bump sensors, cameras, inertial measurement units, odometersand ground speed sensor and compass.

The mobile robot using the data from these sensors in conjunction with amap of the area, stored travel information and location calculations toaugment the location and speed of the mobile robot

Then the microcontroller system taking data from the additional sensorsto allow estimation of speed and heading.

The microcontroller then calculating a projected location based uponelapsed time, speed and heading.

The radar sensors then continually reading mobile robot position basedupon feedback from the microcontroller calculations, allowing forestimation of the position of the mobile robot from the combination ofheading information, time information, speed information and readingsfrom radar system indicating the location of the mobile robot, whereinthe readings are taken at different times.

The system further having a camera or cameras external to the mobilerobot wherein the camera can validate the results of the radar sensorsto verify the distance from the cameras to the mobile robot.

Using a known location of the cameras or cameras relative to the radarsystem sensor or sensors in order to calculate a correction of thelocation of the mobile robot.

Additionally adding an Ultra Wide Band RFID tag to the mobile robotwhich can be read by the same radar signal sensor to identify the mobilerobot and triangulate or trilateralize its position.

Further adding a RFID tag placed in a known location in the yard and aRFID reader for reading this tag in order for the system to allowself-calibration of the distance measurement from the robot to the tag.

Additionally the tag could be a metal spike or plate and a magneticsensor contained within the mobile robot for locating the metal plate.

Additionally the calibration tag could be a chemical tag and the mobilerobot could contain a unique chemical sensor wherein the mobile robotcan determine its proximity to the chemical tag.

Additionally, the sensor data could be filtered using techniques,including Kalman filters, particle filters, Bayesian filters and otherwell-known filtering techniques

In accordance with one embodiment, a system for determining the locationof a mobile robot relative to two distance sensing elements with a knownlocation and separation includes one or more of the following elements.

At least one mobile robot.

A programmable microcontroller system.

A wireless communication system.

At least one distance measurement sensor.

At least one camera external to the mobile robot.

At least one variable reflectance base station at a known location.

Optionally a known fixed reference object identified during the systemsetup.

At least one charging station.

A wireless user interface control.

The microcontroller system being programmed to employ the distancemeasuring sensor to measure the distance to a variable reflectance basestation.

The microcontroller system being programmed to record images from thecamera system.

The microcontroller system being programmed to control the reflectanceof a variable reflectance base station.

The microcontroller being programmed to command the camera to turn to anorientation and position capable of allowing the variable reflector tobe identified.

The microcontroller system being programmed to receive into a memorysystem a map of a work area.

The microcontroller being programmed to vary the scan angle of thecamera to locate the variable reflector while continuously varying thereflector system in order to locate the reflectors.

Once the reflector is identified, the microcontroller being programmedto measure the distance from the robot to the variable reflector.

The microcontroller being programmed with the location or angle of theat least one reflector or reflectors and the optional known fixedobject.

The microcontroller being programmed to calculate the location of themobile robot based upon the distances and angles of the robot to thefixed location and at least one variable reflector.

The microcontroller being programmed to identify the robot location on amap stored in a memory device based upon the location of the robot andthe location.

The microcontroller being programmed to plan a path to a next locationbased upon the comparison of the map location, past map locations anddesired work area.

The microcontroller being programmed to operate a work element such as agrass cutting system only in areas identified on the stored map as workareas based upon the estimated position of the mobile robot ascalculated by the microcontroller system.

The microcontroller system being programmed to return the mobile robotto a known location for service or re-energizing based upon a schedule,battery voltage, current storage level or blade sharpness criteria asidentified by the robot sensor systems.

The microcontroller system being programmed to store work areascompleted and work areas not completed based upon location and operationof the mobile robot and the location information derived from thevariable reflectors and the distance sensors.

The microcontrollers system being programmed to return the mobile robotto the work area in a sub-set of areas of uncompleted work in order tocomplete all of the tasks in the programmed work area.

The microcontroller system being programmed to return to the fixed basestation or programmed end location on the system map after a second maprecording the areas of completed work is equal to the programmed map ofthe required work area.

One aspect of the disclosed technology relates to an autonomous mobilework system for performing work in a user selected area, comprising: amobile work system comprised of a sensor configured to locate a variablereflectivity base station and measure the distance to said base station;and at least one variable reflectivity base station.

In accordance with one feature, the autonomous mobile work systemincludes at least one charging base station.

In accordance with one feature, at least one of said base stations is acharging base station.

One aspect of the disclosed technology relates to a unified workapparatus comprising: an autonomous mobile work system comprised of asensor configured to locate a variable reflectivity base station andmeasure the distance to said base station; and at least one variablereflectivity base station.

In accordance with one feature, the unified work apparatus includes atleast one charging base station.

Another aspect of the disclosed technology relates to a method ofdetermining the location of an autonomous mobile work device. The methodincludes providing a first and second variable reflectivity base stationand an autonomous mobile work device, wherein said autonomous mobilework device is configured to determine the distance between said basestation and said autonomous mobile work system; providing the locationand orientation of a first variable reflective base station to saidautonomous mobile work device; providing the location and orientation ofa second variable reflective base station to said autonomous mobile worksystem; changing the reflectivity state of said first base station;calculating the distance between said first base station and saidautonomous mobile work system; changing the reflectivity state of saidsecond base station; calculating the distance between said second basestation and said autonomous mobile work device; and calculating thelocation of said autonomous mobile work device using the calculateddistances between said autonomous mobile work device and said first andsecond base stations.

Another aspect of the disclosed technology relates to a method ofdetermining the location of an autonomous mobile work device comprising:providing a first and second variable reflectivity base station and anautonomous mobile work device, wherein said autonomous mobile workdevice is configured to calculate the distance between said base stationand said autonomous mobile work device; obtaining the distance betweensaid autonomous mobile work device and each of the first and second basestations; and calculating the location of said autonomous mobile workdevice using the calculated distances between said autonomous mobilework system and said first and second base stations.

Another aspect of the disclosed technology relates to a method ofdetermining the location of an autonomous mobile work device comprising:calculating the location of said autonomous mobile work device using acalculated distance between the autonomous mobile work device and afirst variable reflectivity base station and a calculated distancebetween said autonomous mobile work device and a second variablereflectivity base station.

Another aspect of the disclosed technology relates to a method ofdetermining the location of an autonomous mobile robot devicecomprising: using reflectivity to calculate the location of saidautonomous mobile robot device.

The figures illustrate exemplary aspects of the disclosed technologydescribed above in more detail.

FIG. 1 is a flow chart representing aspects of an exemplary method fordetermining the distance between the variable reflectors and the mobilework system in accordance with one exemplary embodiment. As is describedmore fully above, one or more of the illustrated steps can be omittedwithin the scope of the disclosed technology.

FIG. 2 and FIG. 3 are diagrammatic representations of the system in afirst state with equal reflection, a second state where the reflectionof one reflector has changed between a first and a second state, a thirdstate where the first reflector has returned to its original state and afourth state where a second reflector has changed to a differentreflective state.

FIG. 4 is a diagrammatic illustration of an exemplary system withmultiple reflective states for each variable reflector.

FIG. 5 is a diagrammatic illustration showing that variable reflectorsmay be moved by the user or by the mobile work system to allow for largecoverage areas in accordance with one exemplary embodiment.

FIG. 6 is a diagrammatic illustration showing swarms of autonomousmobile work devices, each with variable reflectors and reflectionsensors with optional non autonomous variable reflectors in accordancewith one exemplary embodiment.

FIG. 7 is a diagrammatic illustration of an exemplary mobile work deviceand an exemplary variable reflector base station in accordance with oneexemplary embodiment;

FIG. 8 is a diagrammatic illustration showing one system for creating avariable radar reflector in accordance with one exemplary embodiment.

FIG. 9 is a diagrammatic illustration showing an optical variablereflector based upon bi-stable display technology such as bi-stablecholesteric LCD technology in accordance with one exemplary embodiment.

FIG. 10 is a diagrammatic illustration showing calibration of the mobilerobot location using a known location tag and onboard tag sensor with acombination of cameras, radar systems or both in accordance with oneexemplary embodiment.

Although the disclosed technology has been shown and described withrespect to a certain preferred aspect, embodiment or embodiments, it isobvious that equivalent alterations and modifications will occur toothers skilled in the art upon the reading and understanding of thisspecification and the annexed drawings. In particular regard to thevarious functions performed by the above described elements (components,assemblies, devices, members, compositions, etc.), the terms (includinga reference to a “means”) used to describe such elements are intended tocorrespond, unless otherwise indicated, to any element which performsthe specified function of the described element (i.e., that isfunctionally equivalent), even though not structurally equivalent to thedisclosed structure which performs the function in the hereinillustrated exemplary aspect, embodiment or embodiments of the disclosedtechnology. In addition, while a particular feature of the disclosedtechnology may have been described above with respect to only one ormore of several illustrated aspects or embodiments, such feature may becombined with one or more other features of the other embodiments, asmay be desired and advantageous for any given or particular application.

What is claimed is:
 1. An autonomous mobile work system for performing work in a user selected area, the system comprising: a mobile work device including a sensor configured to locate a variable reflectivity base station and measure the distance to said base station; and at least one variable reflectivity base station, wherein the mobile work device is configured to transmit a first command that changes an optical and/or an electromagnetic reflectivity state of the at least one variable reflectivity base station; determine a first reflectivity measurement; transmit a second command that changes the optical and/or electromagnetic reflectivity state of the at least one variable reflectivity base station; determine a second reflectivity measurement; and identify the at least one variable reflectivity base station based on the first reflectivity measurement and the second reflectivity measurement.
 2. The autonomous mobile work system of claim 1, comprising a plurality of variable reflectivity base stations, wherein at least one of the plurality of variable reflectivity base stations is a charging base station.
 3. The autonomous mobile work system of claim 1, wherein the variable reflectivity base station changes an optical reflectivity state.
 4. The autonomous mobile work system of claim 1, wherein the variable reflectivity base station changes an electromagnetic reflectivity state.
 5. The autonomous mobile work system of claim 1, wherein the first command comprises at least one of an external command and a predetermined time schedule.
 6. The autonomous mobile work system of claim 1, wherein the second command comprises at least one of an external command and a predetermined time schedule.
 7. The autonomous mobile work system of claim 1, wherein the mobile work device includes a wireless communication interface, and wherein the mobile work device is configured to transmit at least one of the first command and the second command via the wireless communication interface.
 8. The autonomous mobile work system of claim 1, wherein the at least one variable reflectivity base station includes a wireless communication interface, and wherein the at least one variable reflectivity base station is configured to receive wireless signals from the mobile work device.
 9. The autonomous mobile work system of claim 1, wherein the mobile work device includes a variable reflectivity indicator, the variable reflectivity indicator being configured to change its optical and/or electromagnetic reflectivity state.
 10. The autonomous mobile work system of claim 9, wherein the at least one variable reflectivity base station comprises a sensor configured to detect a reflectivity of the variable reflectivity indicator of the mobile work device, and to identify the mobile work device based at least in part on the detected reflectivity. 